The present invention relates to helical scan VTRs (video tape recoders), and more particularly, to a system for achieving color "moviola" (playback faster or slower than the recorded speed) with such a VTR.
When editing a recorded video tape, it is customary to run the tape back in either direction at tape speeds other than the recorded speed, while the headwheel rotational speed is generally the same as the rotation speed used during recording in order to provide the same field rate as used in recording, all while viewing the reproduced signal. This is the so-called "moviola mode". When using the moviola mode, each of the playback heads scans across several tracks, thereby reproducing only a segment of any particular prerecorded track.
If the tape was recorded using separate tracks for the luminance (Y) and chroma (C) signals, then in non-moviola mode playback when the playback speed equals the recording speed, two playback heads are used to reproduce said tracks, respectively. However, when in the moviola mode, it is customary to switch the input of a Y signal demodulator between the Y and C playback heads so that as the Y head moves off the Y track and the C head moves onto the Y track, the Y demodulator input is switched from the Y head to the C head. Similarly, as the C head moves off the Y track and the Y head moves back onto the Y track, the Y demodulator input is switched from the C head back to the Y head. Thus a substantially continuous Y signal is present at the input of the Y demodulator. In other words, whichever head is over the Y track provides the Y signal to the Y demodulator. No input signal is provided to the C demodulator.
The result is a monochrome signal present at the output of the Y demodulator, whose quality is sufficient for editing purposes. However, the monochrome signal causes tape editor fatigue.
It is therefore desirable to provide a color signal from a VTR when in the moviola mode to reduce editor fatigue.